Walter s



Patented Nov. 16,- 1926.

UNITED sT rEs' PATENT o FicE.

WALTER S. LANDIS, F WHITESTONE LANDING, NEW YORK, AND,GUY H. BUCHANAN,

OF WESTFIELD, NEW ERSEY, ASSIGNORS TO AMERICAN CYANAMID COMPANY, OF NEW YORK, N. Y., A CORPORATION OF MAINE.

METHOD OF FUMIGATION.

No Drawing.

This invention relates to a method of fumigating with highly poisonous fumi gants, and has for its object to improve certain of the methods heretofore proposed and now in wide use to the end that they may be made more efficient and less dangerous than they are as at present practiced.

\Vith these and other objects in view, the invention consists in the novel steps and combinations of steps constituting the method, all as will be more fully disclosed below and particularly pointed out in the claims.

In order that the precise nature of the invention may be the more clearly understood, it is said: I

In the fumigation of buildings, ships and other enclosed spaces with hydrocyanic acid gas for the purpose of destroying-vermin and other tests, the common practice has been to determine the volume of the space to be fumigated and then to atomize or vaporize into this space .a suitable quantity of.

liquid hydrocyanic acid. The enclosed space, charged with the fumigant, is'permitted to stand for a suitable length of time, usually one or two hours, or even longer in the case of certain special work, and is then opened up and the poisonous fumigant displaced by the admis-- sion of fresh air from the outside. Where adequate means of ventilating the enclosed space are at hand, the dissipation of the )OlSOIlOllS fumes is not a difficult problem, hut in the case of ships and warehouses from five to twelve hours or longer are usually required I to effectually remove the poisonous gas and render the space habitable. The long time necessary for clearing 40 out the hydrocyanic acid fumes where facilities for ventilation are limited, is at times a source of considerable. annoyance and expense. In the case of a cargo carrying steamship, for example, itmay mean a delay in unloading or re-loading of the ship and a very considerable demurrage charge may accrue due to this tie-up of the vessel. Vi e have found, however, a simple and expeditious method of destroying the residso ual hydrocyanic acid so as to eliminate it in a compartively short time, thereby gaining the use of the space to be fumigated much more quickly than would otherwise be the ca e Application filed July 8, 1921. Serial No. 483,264.

Thismethod consists briefly in the admis-' sion to the space after fumigating, of a volatile aldehyde and steam or water vapor. Aldehyde vapor, such, for example, as that of formaldehyde, reacts only very slowly on dilute gaseous hydrocyanic acid, but if it i is in suflicient concentration and is m the presence of water vapor, the reaction takes place relatively rapidly and is remarkably complete. For example, in carrying out this process, we close up the space to' be fumigated comparatively tightly, and introduce into this space sufiicient hydro.- cyanic acid for an efiective fumigation. This quantity is such; as to provide from,- say, 0.2 volume per cent up to one volume .per cent of hydrocyanic in the space to be fumigated, and the application may be made by generating the gas directly in the space or by using liquid hydrocyanic acid which is applied through one of the several forms of Well known applicators which may be provided for this purpose. We leave the space closed for. one or two hours or whatever time is necessary, to insure killing of the pests present. At the end of this time, We introduce into said space, for"example, to each pound of anhydrous hydrocyanic acid, approximately five pounds of U. S. P. formalin, or its equivalent, in the form of formaldehyde gas. This can be introduced either byatomizing the formaldehyde, or

by pouring the same rapidly onto a quantity I of permanganate crystals. Along with the formalin or formaldehyde gas, we also in.

Under the foregoingcircumstances, the hydrooyanic acid is very quickly destroyed.

For example, in our experimental work, we have destroyed the hydrocyanic acld gas in' a room containing 5,000 parts of said gas per million down to less than 12parts per million inside of one hour by this procedure. In the first ten minutes after introduction of the formaldehyde and water vapor, there was only fifty parts per million of hydrocyanic gas left in the room. Without the addition of the water vapor, which in this instance, serves as an accelerator, our experiments have shown th t w l e less than, onethird of the hydrocyanic acid in five hours.

It is self-evident that one may vary the procedure as above outlined without departing from the spirit of the invention, and we therefore do not wishto be limited to the above disclosure except as may be required by the claims.

What we claim is:

1. The method of fumigating with a highly poisonous fumigant which consists in introducing hydrocyanic acid gas into the space to be fumigated; and subsequently introducing into said'space a volatile aldehyde adapted to normally react relatively natures. WALTER S. LANDIS. GUY H. BUCHANAN. 

